A prospective study of the hemodynamic and renal changes was undertaken in 11 neonates whose mothers were treated with acebutolol for hypertension during pregnancy, compared with a control group of 11 infants born to normotensive mothers. Monitoring of the cardio-respiratory system was performed for a period of 4 days. Renal function was studied during 2 periods (12-36, 60-84 hours of life). Hemodynamic failure was observed in 5 of 11 children from treated mothers. The data concerning the renal function of treated group showed: 1) a diuresis significantly lower during the first period (p less than 0.05); 2) the absence of significant rise in the glomerular filtration rates during the second period; 3) a lower sodium balance during the 1st and 2nd periods (p less than 0.02 and p less than 0.05), a lower calcium balance during the 1st period (p less than 0.01). No relationship was found between the renal changes and the hemodynamic disturbances. The direct effect of the drug on the glomerular and tubular functions and/or the renal arteriolar vasomotricity could explain these changes in the renal function in the newborns prenatally exposed to acebutolol.